This invention relates to vacuum cleaners and more particularly to an indicator for detecting when a clogged condition exists in the intake air passage of a vacuum cleaner and for bleeding ambient air into the suction chamber when such a condition exists for cooling the suction creating motor blower to prevent failure by overheating.
During the operation of a vacuum cleaner, dirt laden air is drawn into the cleaner inlet, directed through a dirt collecting filter bag and clean filtered air is exhausted through an outlet. In U.S. Pat. No. 4,020,525, an indicator for detecting when the dirt collecting filter bag is effectively full and should be changed is disclosed. In that system, the pressure drop across the filter bag is monitored to signal the operator to change bags. As the bag fills, the pressure in the bag increases (suction decreases) and the pressure in the bag chamber decreases (suction increases). In many cases, however, it has been found that the operator of the cleaner ignores the bag change indicator. The continued use of the cleaner under these conditions can result in excessive motor overheating. The high resulting temperatures has in certain cases caused the cleaner housing to structurally weaken, and due to the low pressures within the housing to plastically deform. Further operation of the cleaner may create an excessively hazardous situation. Moreover, some objects that may be picked up by the cleaning tool at the end of the hose may be such as to wedge in and cause a clogging of the hose. When this occurs, the bag condition indicator will not actuate unless the clogging is at the mouth of the bag. In either event, however, merely changing the bag will not alleviate the condition. The operator needs more information to locate the problem which if not corrected can cause overheating of the motor and result in the above described conditions.